I purchased new memory and a new SSD for an early 2011 MacBook Pro, based on an article I saw. My computer was running so slowly, I was ready to junk it. But after reading that article I decided to try a similar upgrade and for a very reasonable price, my computer runs better now than it did when it was new. (I did double the installed RAM and the old drive was a standard disk, not SSD.)
I found the videos for installing both the memory and disk extremely helpful.
I was considering donating my old computer--now I might just keep it as a backup.